1. Field of Invention
The present invention relates to the field of water jet cutting. More particularly, the present invention relates to a hand-held device for cutting by means of high pressure water and methods for using said tool for cutting soft, deformable materials such as automotive floor mats, foams, plastics, rubber, composites, food products and the like.
2. Description of the Related Art
Cutting various materials by means of jets of high pressure water is a well known technique in modern manufacturing engineering. Focused jets of high pressure water from 2,000 pounds per square inch pressure ("psi") or less, up to 60,000 psi or more, are capable of cutting virtually any material. Thick sheets of steel are capable of being cut by means of high pressure water, as are much thinner sheets of soft or sticky material inconveniently cut by mechanical means. Cutting by means of water jets has several advantage including: sufficiently high quality cut providing for sharp inside corners, reduction in or elimination of slag or burr following the cutting operation (typically requiring a subsequent "deburring" operation following conventional cutting procedures), highly accurate contouring resulting in less wasted material, and water jet cutting allows the cut to be initiated at any point along the path to be cut on the workpiece.
The customary term in the field is "water jet cutting." However, abrasive additives may be added to the stream of water comprising the jet to increase cutting effectiveness (although wear on the nozzle is likewise increased). For the cutting of metals, abrasive grit is typically added to the stream after the jet is formed but prior to the impact of the jet on the workpiece. Water jets including abrasives can accomplish the cutting of intricate slots, through cuts and curves cut in metals, glass, stone, composites and similar materials.
Fluids other than water can also be employed if materials cannot be in contact with water but cutting with a jet of fluid is still the preferred cutting technique. For economy of language we will refer herein to "water jet cutting" or "high pressure water" and the like, not intending to exclude cutting by jets of fluid other than water, and not intended to exclude jets of fluid containing abrasive or other additives.
The typical technique for cutting by means of water jets is to mount the piece to be cut (hereinafter "workpiece") in a suitable jig, die or other means for securing the workpiece into position. One or more water jets are typically directed onto the workpiece to accomplish the desired cutting, generally under computer or robotic control. The cutting power is typically generated by means of a single intensifier connected to the cutting head through high pressure tubing, hose, piping, accumulators and filters. Typical units may have powers of 20 horsepower ("hp"), 50 hp, 60 hp up to 75 hp.
The typical mode of water jet cutting is to employ a single water jet cutting head, but this is not an inherent limitation. A fine stream of water, typically travelling at two to three times the velocity of sound, is directed onto the workpiece. The stream of cutting fluid is typically pinhole size in diameter, but a jet slightly larger than (1/16) inch in diameter produces nearly 50 hp when concentrated. Hereinafter we will refer to workpiece and cutting tool in the singular, not intending thereby to exclude the use of a plurality of cutting heads and/or a plurality of workpieces.
It is not necessary to keep the workpiece stationary and to manipulate the water jet cutting tool. The workpiece can be manipulated under a stationary cutting jet, or both the water jet and the workpiece can be manipulated to facilitate cutting. However, increasing the separate degrees of motion to be executed by the workpiece and/or cutting head, increases the complexity of the robotic manipulation system.
This automated cutting process has some drawbacks as conventionally implemented. Among these are the need for mounting the workpiece for processing and removing the cut portions following processing. These steps can increase processing time, although typically several workpieces may be mounted at once for sequential or concurrent processing in the water jet cutting apparatus. Another disadvantage lies in the need for reasonably precise specification of the path the cutting apparatus is to take over the workpiece. The location of the cutting jet in space and the direction of the exiting jet require, in general, six numbers for complete specification; three for location in space and three for orientation. Additionally, the path of movement must be specified which, in its full generality, requires the specification of each of the six spacial and angular orientation coordinates as functions of time. This is most commonly accomplished by means of CAD/CAM programming to identify and plot the passage of the water jet cutting head over the workpiece so as to produce the desired finish form and edge quality.
Jet on-off controls must also be specified as well as any pressure changes of the cutting fluid that are made during the cutting process. Thus, robotic control of the process may be a complex procedure, justified if numerous workpieces of the same geometry are to be processed in the same way.
A more serious drawback to robotic or automated water jet cutting is the variability in dimension and characteristics from workpiece to workpiece. This disadvantage shows itself quite clearly in the process of cutting materials for use as floor mats in cars, trucks and other vehicles. These materials tend to have small (but important) variations in dimension from workpiece to workpiece even when processed in the same manner prior to cutting. These variations can occur from irregular quantities of individual compounds being mixed to produce the workpiece, although understanding the source of such imperfections and variations in the workpieces is not necessary in the practice of the present invention.
These materials are also subject to deformation and changes in dimension during processing, making reproducible cutting difficult by means of robotic or computer controlled water jets. Individual compounds in the workpiece may react differently to various processing conditions, tending to fuse the material through heating and deform during the cool-down period following processing. Additionally, these materials must typically be cut in locations and along paths not easily accessed by means of computer controlled cutting jets.
The present invention contemplates a new and improved hand-held tool for cutting with high pressure water that is simple in design, effective in use, and overcomes the foregoing difficulties and others while providing better and more advantageous overall results.